The invention concerns room air conditioning and filtration equipment, and in particular is directed to a portable or mobile unit that provides for energy recovery ventilation, and which can operate in a positive pressure mode, a negative pressure mode, or a neutral pressure mode. The invention is also concerned with units that clean and condition the room air as well as remove and/or kill airborne pathogens. The unit can be provided with wheels or casters that facilitate bringing the unit into the conditioned space, and can employ intake and exhaust ducts to bring in fresh air and exhaust stale room air, and also conduct a flow of outside air over the air conditioning condenser to remove waste heat to the outdoors.
High Efficiency Particulate Air (HEPA) filters are used extensively in industrial, commercial and residential applications to filter out dust, dirt, and other allergens from the air which can harbor harmful bacteria or other micro-organisms. These filters are capable of filtering out more than 99.99% of the particles in the air.
Recently, due to outbreaks of contagious viral and bacterial diseases, and due to the increase in the incidence of asthma, there has been a heightened concern about contaminants in the indoor air, and about the ability to exclude or confine contaminants in a given area. The need for emergency isolation facilities may well exceed the capacity of area hospitals and clinics, and this may require use of hotel rooms or private spaces to confine infected patients or to protect the more vulnerable patients from airborne infection. In an emergency, it is expected that it will become necessary to isolate at least some of the patients. Some patients will need to be isolated in a fashion to keep any airborne contaminants within a confined area to protect others from the contagion. Other patients, e.g., burn patients, will need to be protected from outside contaminants reaching the patient area. Hospitals lack sufficient spaces that can be used for isolation of patients, whereas the need to isolate patients from the general public or from one another is critical in controlling the situation, thus requiring surge capacity facilities in addition to traditional hospitals.
Most hospitals today have only a few isolation rooms out of the hundreds of patient rooms in the facility. One reason for this is because isolation rooms are very expensive to build as they conventionally require separate, independent HVAC systems for each room to prevent the spread of contaminants to other areas of the hospital. In those cases where the patient is susceptible to contaminants, the room must operate at a positive pressure, whereas when the patient is infected with a contagious pathogen, the room must be under a negative pressure to protect other patients and hospital workers. However, even with isolation HVAC systems the rooms are not easy to convert from positive pressure to negative pressure or vice versa. These rooms are generally built either for positive pressure only or for negative pressure only, and this limits the flexibility of a hospital to deal with emergency situations.
It may also happen that private individuals may need to convert a room in their home to an isolation room. In that case, it would be desirable to be able to use the same equipment also as a normal air conditioner to create a comfortable, clean, and healthy living space when isolation is not needed.
The inventor herein proposes an air conditioner with a heat recovery ventilation or energy recovery ventilation feature, in which some outside air is exchanged with some part of the circulating indoor air, so that the occupants of the conditioned comfort space are provided with fresh air, and the burden of having stale unhealthy air is alleviated. The addition of an energy recovery heat exchanger core, together with suitable fans or other circulating equipment, makes it possible also to control room air pressure, relative to ambient or outside air pressure. In other words, the conditioned comfort space may be provided with neutral pressure (equaling outside air pressure), a negative pressure relative to outside air pressure, or a positive pressure relative to outside air pressure.
Air filtration units, known commercially as HEPAir units, are used extensively in clean room situations to control airborne contaminants while maintaining temperature and humidity control for critical processes such as the sterile packaging of medical devices or pharmaceuticals. These units are also used extensively in the manufacture of semiconductor devices. Units of this type are not usually available as simple portable air conditioning units, but are industrial in nature and capable of handling relatively large volumes of air against a high static pressure such as that encountered with high efficiency particulate air (HEPA) filters, and are capable of attaining an air exchange rate that is sufficient to assure dilution and purge. Accordingly, typical room air conditioning systems have not provided adequate filtration for purposes of trapping and removing viruses, bacteria, or similar airborne pathogens.